|
Interpillary Distance (PD)
PURPOSE To determine the distance in millimeters between the entrance pils of the two eyes for a given viewing distance．
EQUIPMENT
·An easy-to-hold ruler marked in mm.
SET-UP
·The examiner sits directly in front of the patient at eye level．
·The examiner’s face should be located at the patient’s customary near working distance(usually 40 cm)．
STEP-BY-STEP PROCEDURE
FOR NEAR PD
1．Close your right eye and instruct the patient to look at your open left eye，the tip of your nose, or some other near target．Align the zero-point of the ruler on a landmark of the patient’s right eye．Stabilize the ruler by resting two or three fingers on the patient’s face and by lightly resting the ruler on the bridge of the patient’s nose．
2．Still using your left eye, measure to the corresponding landmark on patient’s left eye．For example, if you set the zero on the nasal pillary edge of the patient’s right eye, measure to the temporal pillary edge of his left eye(see Figure 2-13)．
FOR DISTANCE PD
3．Instruct the patient to look at your open left eye．Close your right eye．
4．Align the zero-point of the ruler on a landmark of the patient’s right eye(eg，nasal pillary edge)．Stabilize the ruler by resting two or three fingers on the patient’s face and by lightly resting the ruler on the bridge of the patient’s nose．
5．Close your left eye．Instruct the patient to look at your now open right eye．
6．Measure to the corresponding landmark on the patient’s left eye，as described in step 2 above．
7．Recheck the entire procedure．
Note：By following steps 3 through 7, although the patient never looks at distance, you measure his distance PD, with each eye pointing straight ahead，as if the patient had been looking at distance (see Figure 2-14)．
RECORDING
·Write the distance PD in mm, a slash, then the near PD in mm．
Note：Although you measure the near PD before the distance PD，record the distance PD followed by the near(see Examples)．
·Sometimes the eyes are not centered with respect to the nose, and separate, monocular PD’s are recorded for each eye relative to the center of the bridge of the patient’s nose．
EXAMPLES
·64/61
·62/58
·0D 30/28 0S 32/30
EXPECTED FINDINGS
·The average measurement for adults is 64/60 |
